FR3068606A1 - PROCESS FOR PREPARING DRY EMULSIONS FROM BIOSOURCE PARTICLES - Google Patents

Abstract

The present invention relates to a method for preparing a dry emulsion, comprising a step of drying an oil-in-water Pickering emulsion containing vegetable powder particles. It also relates to dry emulsions obtainable by said process.

Description

PROCESS FOR THE PREPARATION OF DRY EMULSIONS FROM BIOSOURCED PARTICLES

The present invention relates to a process for the preparation of dry emulsions from an emulsion obtained from biobased particles. It also relates to the dry emulsions thus obtained and their uses, preferably in the cosmetic, food industry or in bitumen, as well as a process for the redispersion of said emulsions and the redispersed emulsions.

An emulsion consists of a mixture of two liquids immiscible with each other, made stable over time using an emulsifier. Emulsions are generally divided into two categories, so-called "water-in-oil" emulsions, where water droplets are suspended in an oily phase, and so-called "oil-in-water" emulsions, where oil droplets are suspended in an aqueous phase. Milk, butter and salad dressing are examples of common emulsions in the food industry.

Emulsifiers, also called emulsifiers, surfactants or surfactants, are compounds capable of stabilizing emulsions over time. These compounds can be of artificial origin, such as synthetic polymers, or of natural origin, such as phospholipids or proteins.

Currently, there is a gradual elimination, especially in the food and cosmetics sector, of synthetic surfactants deemed harmful to health and the environment. There is therefore a real need for new emulsifiers of natural origin (bio-based).

Amphiphilic solid particles are also used to stabilize emulsions. The systems obtained, called Pickering emulsions, are often endowed with an extraordinary kinetic stability (F. Leal-Calderon, V. Schmitt, Solidstabilized emulsions, Current Opinion in Colloid and Interface Science, 13, 217-227 (2008) ). Solid particles are able to adsorb strongly and irreversibly at the interface of immiscible phases, forming a rigid and thick layer capable of lastingly preventing the destruction of emulsions such as drop recombination (coalescence).

It is known that the aqueous phase of the emulsions can be removed by a drying process. We then speak of "dry" emulsions. "Dry" emulsions are powders made up of lipid particles covered with a solid protective zone. Dry emulsions are capable of regenerating oil-in-water emulsions after rehydration and can be transported and stored more easily.

Proteins and galactolipids are known emulsifiers for making dry emulsions. International application WO2014 / 076432 relates to a method for manufacturing a dry emulsion. The emulsifier used is preferably chosen from proteins obtained from whey. The advantage of this emulsion is that it allows the administration of polysaccharides in the food sector.

International application WO2009 / 090249 relates to dry emulsions obtained by using galactolipids as emulsifiers.

International application WO98 / 19652 relates to dry emulsions obtained by using proteins isolated from yellow peas.

An alternative for obtaining stable emulsions over time consists in using amphiphilic solid particles capable of adsorbing at the interface of the two immiscible liquids. Such emulsions are called "Pickering emulsions".

There is currently a need to have stable dry emulsions which can be used in any field of application.

The present invention aims to provide a stable dry emulsion which can be used in various fields of application, in particular cosmetic, food or in bitumen compositions.

Another object of the present invention is to provide a stable dry emulsion which can be satisfactorily redispersed.

Another object of the invention is to provide a process for the preparation of stable dry emulsions from bio-based particles.

Thus, the present invention relates to a process for preparing a dry emulsion, comprising a step of drying an oil-in-water Pickering emulsion containing particles of vegetable powder. The rehydrated dry emulsion has identical (or very similar) characteristics to the oil-in-water emulsion before drying.

The Pickering emulsions used according to the invention comprise particles of vegetable powder, preferably of at least one oleaginous species.

The process of the invention therefore consists in implementing a step of drying these Pickering emulsions.

This process thus makes it possible to obtain dry emulsions having improved stability.

According to one embodiment, the dry emulsions are obtained from Pickering emulsions stabilized by an emulsifier consisting of vegetable powder.

According to a preferred embodiment, the dry emulsions according to the invention are obtained from Pickering emulsions stabilized by an emulsifier consisting of vegetable powder obtained from oilseed meal.

According to a preferred embodiment, the dry emulsions according to the invention contain a protective saccharide compound, in particular chosen from the group consisting of sucrose, lactose, fructose, trehalose, dextrins, maltodextrins, yellow dextrins, invert sugars, sorbitol, polydextrose, starch syrup, glucose syrup and mixtures thereof. Preferably, the protective saccharide compound is lactose.

This embodiment is particularly advantageous in that it makes it possible to obtain even more stable emulsions, and in that the emulsions thus obtained once dried and then redispersed have properties similar to those obtained before drying.

According to one embodiment, the method according to the invention therefore consists in implementing the following steps:

- the preparation of a stabilized Pickering emulsion, and

- the drying of the Pickering emulsion in order to obtain a dry emulsion.

The preparation of the stabilized Pickering emulsion can be carried out by any process known to a person skilled in the art. Preferably, the Pickering emulsion according to the invention is prepared by stirring a vegetable powder in the aqueous phase of the emulsion then addition of the oily phase in order to obtain an "oil in water" dispersion, stabilized by the plant particles. A preferred embodiment of preparation is described below.

The drying of the emulsion can be carried out by any process known to a person skilled in the art. Preferably, the emulsion is dried by lyophilization or by zeodratation, by evaporation in an oven or an atomization tower. Preferably, the emulsion is dried by lyophilization.

According to the invention, the term “zeodratation” designates a dehydration process by using zeolites, materials capable of absorbing the water vapor released by the dried matter.

According to one embodiment, the drying step is carried out by lyophilization.

Lyophilization is a vacuum dehydration process for a product previously frozen by sublimation. This discontinuous process is used in particular in the biochemical, cosmetic, food and pharmaceutical industries to extract a dry product from an aqueous solution. The method comprises a step of freezing the product and then at least one step of drying the product under vacuum. This process stabilizes heat-sensitive products by transforming them into solid powders. The lyophilized product can then be regenerated by simple moistening of the solid powder.

Preferably, the lyophilization drying step according to the invention consists in freezing the abovementioned Pickering emulsion at a temperature between -200 ° C and -18 ° C, preferably at -80 ° C, for a period of time between a few minutes and 24 hours, preferably for 12 hours, then sublime the ice at a pressure between 0.1 mbar and 1mbar, preferably equal to 0.3 mbar, at a temperature between 20 ° C and 35 ° C , preferably 25 ° C, for a period of between 24 and 72 hours, preferably for 24 hours.

According to the invention, the above-mentioned freezing step can be carried out by conventional means or even with liquid nitrogen.

According to another embodiment, the drying step is carried out in an oven.

Preferably, this step consists in placing the abovementioned Pickering emulsion in an oven at a temperature between 60 ° C and 120 ° C, preferably equal to 70 ° C, for a period between 12h and 72h preferably for 12 h.

According to another embodiment, the drying step is carried out by atomization.

Preferably, this step consists of spraying the emulsion into a drying tank. The emulsion / drying air mixture is introduced at a given flow rate via a nozzle or a turbine, at a temperature generally between 110 ° C. and 270 ° C. The outlet temperature of the dry pulverized material is controlled and is generally between 65 ° C and 110 ° C.

According to one embodiment, the above-mentioned vegetable powder is obtained from at least one oleaginous species.

According to one embodiment, the vegetable powder is obtained from seeds of oleaginous species, shells of oleaginous species, dandruff of oleaginous species, oil cake of oleaginous species and their mixtures.

According to a particularly preferred mode, the vegetable powder is obtained from oilseed meal.

Thus, an advantageous method according to the invention consists in preparing a dry emulsion by drying a Pickering emulsion comprising particles of vegetable powder of at least one oleaginous species, preferably of vegetable powder obtained from oil cake of species. oil.

Preferably, the oleaginous species are chosen from the group consisting of rapeseed, sunflower, soybean, flax, hemp, pea, faba bean, lupine, cocoa, castor, olive, l almond, corn germ, poppy, sesame, walnut, oil palm kernel, rapeseed, safflower, and mixtures thereof.

According to one embodiment, the vegetable powder thus obtained is in the form of particles of average size between 0.1 μm and 100 μm, and preferably between 0.5 μm and 50 μm.

According to the invention, the term "average size" designates the number average diameter of the particles.

The particle size distribution is determined by statistical analysis of images (for example by optical microscopy, x60 objective, 2 images of 119x88pm). The largest dimension of all the particles present on the images is noted. The total number of particles measured varies from sample to sample but is never less than 100.

According to one embodiment, in the Pickering emulsions according to the invention, the rate of anchoring of the plant particles at the interface between the two phases of the emulsion is between 60% and 95%, preferably between 70 % and 90%.

The anchoring rate is defined as the mass ratio between the plant particles adsorbed at the interfaces and the particles used to make the emulsion. An anchoring rate of less than 100% reveals the presence of free particles in the continuous phase.

For example, the anchoring rate is determined by weighing the particles not anchored to the surface of the drops. The lipid drops decorated with particles are separated from the aqueous phase containing the particles which are not anchored by natural creaming (approximately 3 days). The cream is removed and the aqueous phase is treated by lyophilization to collect the non-anchored particles which are then weighed. The anchoring rate is calculated by difference:

t _a = 100 * (mass of total particles - mass of non-anchored particles) / (mass of total particles)

According to one embodiment, the Pickering emulsion containing particles of vegetable powder is obtained according to a process comprising the following steps:

a) the preparation of a vegetable powder of at least one oleaginous species;

b) the addition of said vegetable powder in an aqueous phase to obtain a suspension (S), followed by the incorporation of oil in the suspension (S) to obtain an emulsion of oil-in-water type; and

c) the agitation of the emulsion obtained at the end of the previous step.

According to a preferred embodiment, the aqueous phase contains at least one protective saccharide compound. The saccharide compound (s), introduced into the aqueous phase, are chosen from sucrose, lactose, fructose, trehalose, dextrins, maltodextrins, yellow dextrins, invert sugars, sorbitol, polydextrose, syrup d starch, glucose syrup and mixtures thereof.

Step a) of the process described above consists in refining particles of at least one oilseed species, preferably oilseed meal, in order to obtain a vegetable powder.

Preferably, step a) consists of a mechanical treatment step in the dry or wet process. This first step aims to refine the average particle diameter.

Among the mechanical treatments that can be implemented according to the invention, mention may be made of the following techniques: propellers, high pressure homogenization, or even ball or wheel grinding.

Preferably, step a) is carried out using a universal mill.

The term "grinding" means that the material is subjected to striking, shearing and percussion effects within a grinding device.

The term "sieving" means that it is possible to select the desired grinding fineness. In general, the fineness of grinding of the raw material can be chosen between 0.12 and 10 mm by means of interchangeable sieves. The screens commonly used in grinders have openings of 120 µm, 200 µm, 250 µm, 500 µm, 750 µm, 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 8 mm and 10 mm.

Preferably, the grinding and sieving according to step a) are carried out by a grinder at 120 μm.

Thus, step a) makes it possible to obtain a vegetable powder in the form of particles of suitable size.

According to one embodiment, the vegetable powder thus obtained is in the form of particles of average size between 0.1 μm and 100 μm, and preferably between 0.5 μm and 50 μm.

According to the invention, the term "average size" designates the average diameter of the particles.

The particle size distribution is determined by statistical analysis of images (for example by optical microscopy, x60 objective, 2 images of 119x88pm). The largest dimension of all the particles present on the images is noted. The total number of particles varies from sample to sample but is never less than 100.

Preferably, the refining consists of a step of grinding and sieving oilseed meal in order to obtain a vegetable powder.

The vegetable powder obtained after step a) is preferably produced from sunflower, cocoa, rapeseed or lupine cake.

The term “oil cake” designates solid co-products obtained after grinding the oil seeds and solvent extraction of the oils. Oil cakes are generally valued as a source of protein food for livestock. The cakes thus obtained are then ground and sieved in order to produce a powder.

Step b) of the process described above consists in adding the powder obtained at the end of step a) in an aqueous phase to prepare an emulsion.

Step b) consists in adding the vegetable powder in an aqueous phase to obtain a suspension (S) followed by the incorporation of oil in said suspension (S), to obtain an oil-in-water emulsion.

Preferably, the emulsion contains from 5% to 40% of oil and from 60% to 95% of water, more preferably from 10% to 30% of oil and from 70% to 90% of water, by relative to the total weight of said emulsion.

According to one embodiment, the aqueous phase of the emulsion is buffered. Preferably, the aqueous phase has a pH of between 5 and 9, more preferably between 6 and 8.

The buffer used can be any type of buffer. Preferably, the buffer used is an inorganic salt and / or a mixture of inorganic salts, more preferably the buffer contains at least contains 0.1 M of phosphate buffer (KH ₂ PO ₄ / K ₂ HPO ₄ ).

According to one embodiment, the aqueous phase contains between 0% and 20% by mass of protective saccharide compound, preferably lactose, preferably 18% lactose.

Step c) of the process described above consists in adding energy to the mixture obtained at the end of step b), containing the vegetable powder, in order to obtain a stabilized emulsion.

By definition, an emulsion consists of fine drops of a phase dispersed in a continuous dispersing phase, immiscible with the first.

Step c) consists in supplying energy to the emulsion obtained at the end of step b) to stabilize said emulsion. Such a step can also be assimilated to an emulsification step.

Step c) can be carried out by various means.

According to one embodiment, step c) is carried out by means of an agitator of the rotor / stator type.

Generally, a rotor / stator agitator comprises a movable part, called rotor, fixed on a stationary part, called stator, and capable of causing agitation in a medium.

According to one embodiment, the stirring step c) is carried out by means of an ultrasonic device.

In general, the use of ultrasound is an efficient and energy-efficient way to provide intense mechanical stress and energy to mixtures of solutions such as powder and liquid mixtures.

According to one embodiment, step c) is carried out using a high pressure homogenizer.

In general, a high pressure homogenizer is a device comprising numerous pistons which make it possible to vary the pressure within the medium, causing vacuum effects, training effects and or shearing effects.

Preferably, the homogenization pressure of the high pressure homogenizer is between 50 bar and 1000 bar, preferably between 100 bar and 300 bar.

The use of a high pressure homogenizer is particularly advantageous in that it makes it possible to obtain finer powder sizes and smaller drop sizes. This embodiment thus makes it possible to obtain more stable emulsions over time.

According to one embodiment, the stirring step c) is carried out by means of a ball mill.

In general, ball mills are devices capable of grinding, involving the effects of friction and multiple impacts between the sample, the balls and the internal walls of the bowl or mortar. Ball mills are devices suitable for the mixing and homogenization process.

According to a preferred embodiment, the invention relates to a method for preparing a dry emulsion, comprising a step of drying a Pickering emulsion containing particles of vegetable powder, said Pickering emulsion being obtained according to the above-mentioned method, in which step c) of agitation is carried out by means of a high pressure homogenizer.

The use of a high pressure homogenizer makes it possible to obtain dry emulsions which have the best stability once redispersed in an aqueous medium.

The present invention also relates to a dry emulsion capable of being obtained according to the method as defined above.

According to one embodiment, the dry emulsions according to the invention have the following physicochemical characteristics:

Rds, the ratio between the mean surface diameters (D _s =

ZNjDj

Nest?

), where Ni is the number of drops of diameter D,), drops of the emulsion before drying and after drying / redispersion, is between 1 and 4, preferably between 1 and 2.

Rûv, the ratio between the mean diameters by volume (D _v =

ZNjDt NtD?

), where N;

is the number of drops of diameter D,), of the drops of the emulsion before drying and after drying / redispersion, is between 1 and 6, preferably between 1 and 4.

- Appearance or not of an oil layer on the surface of the emulsion obtained by redispersion of the dry emulsion.

Redispersion is carried out by simple stirring with a spatula or using a magnetic bar of the dry emulsion in distilled water (buffered to pH 7) or distilled water viscosified with 3% by mass of sodium alginate.

The average diameters of the initial emulsions and of the emulsions obtained by redispersion are determined by laser particle size. The presence of solid particles within the emulsions distorting the conventional particle size measurement, these are detached from the interfaces of the drops by dilution and stirring of the emulsion in a solution containing a surfactant, sodium dodecyl sulfate (SDS), at 10%. By attaching to the interfaces, the SDS causes the desorption of particles. It then becomes easy to separate the drops from the particles by centrifugation. Once the separation has been carried out, the particle size distribution of the drops is measured by laser particle size.

The present invention also relates to the use of a dry emulsion as defined above, in cosmetic, pharmaceutical, agrifood or bitumen compositions.

The present invention therefore also relates to a cosmetic composition comprising at least one dry emulsion as defined above.

The present invention therefore also relates to a pharmaceutical composition comprising at least one dry emulsion as defined above.

The present invention therefore also relates to an agrifood composition comprising at least one dry emulsion as defined above.

The present invention therefore also relates to a bitumen composition comprising at least one dry emulsion as defined above.

The present invention also relates to a process for preparing a Pickering emulsion comprising a step of dispersing a dry emulsion as defined above in an aqueous phase containing water.

This process consists in redispersing the dry emulsions according to the invention in an aqueous phase.

According to one embodiment, this process comprises the addition of water or water viscosified with alginate, followed by manual stirring with a spatula.

The present invention also relates to a Pickering emulsion capable of being obtained according to the above method. The invention therefore also relates to the redispersed emulsions obtained from the dry emulsions according to the invention.

EXAMPLES

Example 1: Preparation of a dry emulsion by a lyophilization drying process

A Pickering emulsion stabilized by 8.8% by mass (relative to the aqueous phase, 7.5% by total emulsion) of defatted rapeseed meal, containing 15% by mass of sunflower oil is obtained by means a high pressure homogenizer. Homogenization is carried out with an inlet pressure of 3.44 bar and with a pressure in the chamber of 801 bar (Microfluidizer M-110S). The emulsion suffers 20 pistons. The device operates in a closed circuit and the emulsion makes an average of 6 passages in the device. This emulsion is placed for 12 hours in a freezer at -80 ° C (Thermo scientific, Forma 900 Sériés) and is lyophilized for 24 hours at 0.3 mbar at room temperature (FTS Systems, Dura-Dry).

The dry emulsion obtained is a stable powder in storage and containing 1/3 of rapeseed meal and 2/3 of sunflower oil in mass proportion.

Example 2: Preparation of a dry emulsion by a drying process in an oven

A Pickering emulsion stabilized by 8.8% by mass (with respect to the aqueous phase, 7.5% with respect to the total emulsion) of defatted cocoa cake, containing 15% by mass of sunflower oil is obtained by means a high pressure homogenizer. Homogenization is carried out with an inlet pressure of 3.44 bar and with a pressure in the chamber of 801 bar (Microfluidizer M-110S). The emulsion suffers 20 pistons. The device operates in a closed circuit and each emulsion makes an average of 6 passages in the device. This emulsion is placed for 12 hours in an oven at 70 ° C (DRY-Line, VWR).

The dry emulsion obtained is a dry powder stable in storage and containing 1/3 of cocoa cake and 2/3 of sunflower oil in mass proportion.

Example 3: Preparation of a redispersed emulsion

A defined quantity of dry emulsion obtained according to Example 1 is added to distilled water containing 3% by mass of sodium alginate. The mixture is homogenized using simple agitation with a spatula.

The redispersed emulsion obtained has the same macroscopic appearance as the emulsion before drying and does not have any oil on the surface.

Redispersed dry emulsion Initial emulsion before drying Average size report D _v in pm 4.6 1.3 Appointment = 3.6 D _s in pm 0.94 0.84 Rds = 1.1

The emulsion before drying and the dry emulsion redispersed in the aqueous phase are observed using an optical microscope. It thus appears that the structure of the starting emulsion is well preserved after drying and redispersion but that a few drops of larger oil are present. These drops of oil are at the origin of the increase in the average diameter measured by laser granulometry.

The volume average diameter, D _v , gives a larger statistical weight to the drops of large diameter, compared to the average surface diameter, D _s . As a result, the R _Dv report is therefore a more "sensitive" indicator than the R _Ds report ·

Example 4: Impact of a saccharide compound such as lactose

During freezing and drying, the drops are concentrated and therefore compressed, which can lead to recombination phenomena (coalescence). It is known that the addition of a saccharide compound improves the protection of emulsions during drying. The polysaccharide would form a secondary protective layer on the surface of the lipid drops, preventing the phenomenon of coalescence.

Pickering emulsions with the following compositions are obtained using a high pressure homogenizer. Homogenization is carried out with an inlet pressure of 3.44 bar and with a pressure in the chamber of 801 bar (Microfluidizer M-110S). The emulsion suffers 20 pistons. The device operates in a closed circuit and the emulsion makes an average of 6 passages in the device (% expressed relative to the total emulsion):

7.5% cocoa, 15% sunflower oil

7.5% cocoa, 15% sunflower oil, 15.5% lactose

7.5% cocoa, 15% sunflower oil, 15.5% lactose. Lactose is added after obtaining the emulsion, just before the drying step

7.5% rapeseed meal, 15% sunflower oil

7.5% rapeseed meal, 15% sunflower oil, 15.5% lactose

These emulsions are placed for 12 hours in a freezer at -80 ° C (Thermo scientific, Forma 900 Sériés) and are zeodrated for 24 hours at 1mbar at 30 ° C (Boncher, Drytech).

These 5 dry emulsions are redispersed according to Example 3.

RUV rûs Lactose-free cocoa 5.9 3.6 Cocoa with lactose 3,7 2.0 Cocoa with lactose 4.0 2.0 added just before drying Lactose-free rapeseed 3.6 1.1 Rapeseed with lactose 1.7 1.1

In all cases, no oil layer is observed on the surface of the emulsion.

The R _Dv and R _Ds ratios are lower in the presence of lactose. The addition of lactose thus improves the resistance of the emulsion to drying + 15 redispersion.

This protector can either be added to the system before making the emulsion or once the emulsion has been obtained, just before the drying step.

Claims (11)

1. A method of preparing a dry emulsion, comprising a step of drying an oil-in-water Pickering emulsion containing particles of vegetable powder. 2. Method according to claim 1, wherein the drying step is carried out by lyophilization, zeodratation, in an oven or by atomization. 3. Method according to any one of claims 1 or 2, wherein the vegetable powder is obtained from at least one oleaginous species. 4. Method according to any one of claims 1 to 3, wherein the aqueous phase contains a protective saccharide compound among sucrose, lactose, fructose, trehalose, dextrins, maltodextrins, yellow dextrins, invert sugars , sorbitol, polydextrose, starch syrup, glucose syrup and mixtures thereof. 5. Method according to claim 3, in which the oleaginous species are chosen from the group consisting of rapeseed, sunflower, soybean, flax, hemp, pea, faba bean, lupine, cocoa, castor oil, olive, almond, corn germ, poppy, sesame, walnut, oil palm kernel, rapeseed, safflower, and mixtures thereof. 6. Method according to any one of claims 1 to 5, in which the oil-in-water Pickering emulsion containing vegetable powder particles is obtained according to a method comprising the following steps: a) the preparation of a vegetable powder of at least one oleaginous species; b) the addition of said vegetable powder in an aqueous phase to obtain a suspension (S), followed by the incorporation of oil in the suspension (S) to obtain an emulsion of oil-in-water type; and c) the agitation of the emulsion obtained at the end of the previous step. 7. The method of claim 6, wherein the stirring step c) is carried out by means of a rotor / stator type stirrer, an ultrasonic device, a high pressure homogenizer or a ball mill. 5 8. Dry emulsion capable of being obtained according to the method according to any one of claims 1 to 7. 9. Use of a dry emulsion according to claim 8, in cosmetic, pharmaceutical, food or bitumen compositions. 10. A method of preparing an oil-in-water Pickering emulsion comprising a step of dispersing a dry emulsion according to claim 8 in an aqueous phase containing water. 11. Pickering emulsion capable of being obtained according to the method of claim 10.